Hermetically-Sealed Feed-Through Device and Method of Assembly

ABSTRACT

A method of making a hermetically-sealed feed-through device includes inserting an elongate conductor or conductors within a hollow portion or portions of a plastic insulator body and inserting the plastic insulator body within a hollow outer jacket to form an assembly. At least one of the conductor or conductors, insulator body, or jacket of the assembly has a plurality of circumferential grooves. Thereafter, the assembly is crimped and/or is swage-crimped at ambient temperature to cause the materials of the conductor or conductors, insulator body, and outer jacket to be displaced or extrude into the grooves thereby creating mechanical interlocks between the conductor or conductors, insulator body, and outer jacket. Additional methods and feed-through devices made by the methods are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending U.S. application Ser.No. 11/968,537, filed Jan. 2, 2008, which claims the benefit under 35USC §119(c) of U.S. Provisional Patent Application No. 60/883,247, filedJan. 3, 2007.

BACKGROUND

The present invention relates to feed-through devices subject to harshenvironments, and more particularly, the present invention relates to afeed-through device, such as an electrical or optical feed-throughdevice, that is hermetically sealed.

An electrical or optical feed-through device enables electrical oroptical continuity from inside a sealed chamber or vessel through a wallof the chamber or vessel to a location external of the chamber orvessel. The feed-through device must be able to withstand the harshenvironment within the chamber or vessel without permitting the creationof leakage paths out of, or into, the sealed chamber or vessel.

Examples of feed-through devices include: terminal feed-through devicesfor lithium batteries and other electrochemical devices having corrosiveelectrolytes; instrumentation electrical and RF feed-through devices forchemical reactor vessels; thermocouple feed-through devices for heattreating atmospheres and vacuum furnaces and environmental testchambers; and electrical power feed-through devices for controlledatmosphere furnaces and ovens. Also, see U.S. Pat. No. 4,982,055 issuedto Pollack et al. which discloses a sealed electrical feed-throughdevice, and U.S. Pat. No. 6,351,593 B1 issued to Pollack et al. whichdiscloses a hermetically-sealed optical feed-through device.

Sealed electrical terminal feed-through devices typically utilizeglass-to-metal, ceramic-to-metal, or molded plastic-to-metal sealtechnologies. The materials from which the terminal and insulatorcomponents of the devices are made are required to have substantiallymatching thermal coefficients of expansion over the end use operatingtemperature performance range of the devices to ensure that hermeticseals are maintained. Accordingly, this limits material choices andperformance capabilities. In addition, the selection of the materialused for the seal components is further limited due to the requiredfabrication process temperatures used during manufacture of the devices;because, the fabrication process temperatures are typically greater thenthe performance operating range of the devices.

Accordingly, there is a need for a feed-through device providingenhanced performance capabilities and a method for making a feed-throughdevice that enables such extended capabilities to be achieved. Themethod of manufacturing the devices should permit the selection ofmaterials for the terminal and insulator components from a wider varietyof materials then currently permitted. The selected materials shouldprovide the device with enhanced corrosion resistance capabilities andshould reduce galvanic-induced corrosion and provide a longer lastingseal.

BRIEF SUMMARY

The present invention relates to a method of making ahermetically-sealed feed-through device. An elongate conductor isinserted within an insulator, and the insulator is inserted within ahollow outer jacket to form an assembly. As an alternative, multipleseparate conductors can be inserted at spaced locations within theinsulator. At least one of the conductor, insulator, or jacket of theassembly has a plurality of circumferential grooves. Thereafter, theassembly is crimped, swage-crimped, or both at ambient temperature tocause the materials of the conductor, insulator, and outer jacket to bedisplaced or extrude into the grooves thereby creating mechanicalinterlocks between the conductor, insulator, and outer jacket.

The operation of crimping, swage-crimping, or both, of the presentinvention includes a first crimping and/or swage-crimping operation inwhich two or more circumferentially-extending crimps are simultaneouslyformed at opposite end sections of the assembly and a separate secondcrimping and/or swage-crimping operation in which at least onecircumferentially-extending crimp is formed at a location on theassembly spaced from and between the circumferentially-extending crimpsformed at opposite end sections of the assembly.

According to a preferred embodiment of the present invention, theinsulator is initially made or provided with at least a pair of spacedcircumferential grooves on its inner surface for facing the conductorand at least three spaced-apart circumferential grooves on its outersurface for facing the outer jacket. Accordingly, during the crimpingand/or swage-crimping operations, the circumferentially-extending crimpsformed during the first operation are formed at locations correspondingto the outer pre-existing grooves on the outer surface of the insulator,and the crimp formed by the second operation is formed at a locationcorresponding to a middle one of the pre-existing grooves on the outersurface of the insulator.

Additional process steps according to the present invention can includeannealing the outer jacket before the step of inserting the insulatorwithin the hollow outer jacket, and annealing the crimped and/orswage-crimped assembly to a temperature below the melting pointtemperature of the insulator.

According to another aspect of the present invention, a method of makinga hermetically-sealed electrical feed-through device includespositioning one or more separate conductors within a separate outer bodyin a mold such that a gap or gaps are formed between the singleconductor or multiple spaced-apart conductors and the outer body.Thereafter, one or more inserts are inserted in the gap or gaps betweenthe conductor or conductors and the outer body, and the gap or gaps arefilled with molten material, such as plastic, such that the plasticencases the insert or inserts within the plastic. When permitted toharden, the plastic connects the conductors and inserts to the outerbody. As an example, the inserts may be made of a ceramic material, ahigh temperature plastic material, or the like. In some cases, crimpingand/or swage-crimping operations can be used to further secure theconductors, plastic insulator, and inserts to the outer body. In othercases, no crimping and/or swage-crimping operations may be required.

According to yet another aspect of the present invention, ahermetically-sealed electrical feed-through device is provided. Thedevice has one or more elongate conductors each having a central sectionbetween opposite exposed ends and an insulator defining one or morehollow channels that confront and cover the central section of each ofthe conductors. An outer jacket confronts and covers the insulator, andat least a pair of spaced-apart outer circumferential crimps is formedin the outer jacket at locations adjacent opposite end sections of theinsulator. In addition, at least one additional circumferential crimp isformed in the outer jacket at a location spaced from and between theouter circumferential crimps.

According to a preferred embodiment, the insulator has at least a pairof spaced circumferential grooves on its inner surface facing theconductor or conductors and at least three spaced-apart circumferentialgrooves on its outer surface facing the outer jacket. The locations ofthe outer circumferential crimps and the one additional circumferentialcrimp correspond to the grooves on the outer surface of the insulator,whereby the outer jacket deflects into the grooves on the outer surfaceof the insulator creating a hermetically-scaled, mechanical interlocktherebetween of high mechanical strength. Extruded portions of theconductor or conductors extend into the grooves on the inner surface ofthe insulator thereby providing hermetically-sealed, mechanicalinterlocks of high mechanical strength between the conductor orconductors and the insulator sleeve.

According to yet another aspect of the present invention, ahermetically-sealed electrical feed-through device is provided thatincludes one or more conductors, a separate outer body, and a plasticinsulator molded in place therebetween. The plastic insulator connects,separates, and suspends the conductor or conductors within the outerbody. A separate insert or separate inserts can be embedded within themolded plastic insulator. As an example, the inserts may be made ofceramic or high-temperature plastic material.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present invention should become apparentfrom the following description when taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of a first embodiment of an electricalfeed-through device according to the present invention;

FIG. 2 is a cross-sectional view of the device of FIG. 1;

FIG. 3 is a plan view of a second electrical feed-through deviceaccording to the present invention;

FIG. 4 is a cross-sectional view of the device of FIG. 3; and

FIG. 5 is a plan view of a third electrical feed-through deviceaccording to the present invention; and

FIG. 6 is a cross-sectional view of the device of FIG. 5.

DETAILED DESCRIPTION

A first embodiment of a feed-through device 10 according to the presentinvention is illustrated in FIGS. 1 and 2. As an example, the device 10can be used as a terminal lead for the positive or negative electrode ofa high voltage lithium-ion cell. Examples of other uses for the device10 include: a terminal feed-through in other electrochemical devices; aninstrumentation electrical and RF feed-through for chemical reactorvessels; a thermocouple feed-through for heat treating atmosphere andvacuum furnaces and environmental test chambers; and an electrical powerfeed-through for controlled atmosphere furnaces and ovens.Alternatively, the device can be an optical feed-through instead of anelectrical feed-through.

The device 10 illustrated in FIGS. 1 and 2 has a center terminalconductor 12 with opposite exposed ends 14 and 16 to which welded and ormechanical connections can be formed on opposite sides of a wall of achamber, vessel, or the like that separates a harsh environment from anadjacent environment. A center section 18 of the conductor 12 is encasedwithin an insulator sleeve 20, and an outer body, covering, or jacket,22 extends over the insulator sleeve 20 and sandwiches the insulatorsleeve 20 between the conductor 12 and the outer body 22. The insulatorsleeve 20 and outer body 22 provide a hermetic seal about the centersection 18 of the conductor 12 to prevent liquids, gases, or otherenvironmental contaminants from passing along the length of theconductor 12 between the engaging surfaces of the conductor 12 andinsulator 20, as well as between the engaging surfaces of the insulator20 and outer body 22.

As best illustrated in FIG. 2, the mating surfaces of the conductor 12,insulator 20, and outer body 22 are non-linear and substantiallyundulate with peaks and valleys between ends 14 and 16 of the conductor12. These non-linear surfaces are formed by crimping and/orswage-crimping operations and function to further reduce the likelihoodof leakage through the assembled device 10. As a result of the crimpingand/or swage-crimping operations, the mating surfaces include a seriesof ridges and grooves tightly meshed together without void spaces. Inthe embodiment illustrated in FIGS. 1 and 2 for example, the centersection 18 of the conductor 16 of the fully assembled device 10 issubstantially cylindrical, except for a spaced pair ofoutwardly-extending circumferential ridges, 24 and 26; the insulatorsleeve 20 is also substantially cylindrical, except for inner diametercircumferential grooves, 28 and 30, and outer diameter circumferentialgrooves, 32, 34 and 36; and the outer body 22 is also substantiallycylindrical, except for an outwardly turned collar 38 at one end thereofand three inwardly-extending circumferential ridges, 40, 42 and 44.

This assembly is made by the following process. The conductor 12,insulator 20 and outer body 22 are produced separately from differentmaterials that can have significantly different thermal coefficients ofexpansion. For example, the conductor 12 can be made of aluminum,copper, titanium, molybdenum, or the like, the insulator sleeve 20 canbe molded of hard plastic, and the outer body 22 can be made ofstainless steel or like material. Of course, other materials andcombinations of materials can be selected for use.

In the embodiment illustrated in FIGS. 1 and 2, the center section 18 ofthe conductor 12, as originally manufactured, can be substantiallycylindrical without ridges or grooves; and likewise, the outer body 22is also originally formed without grooves or ridges. However, theinsulator sleeve 20 can be molded with grooves 28, 30, 32, 24 and 36substantially as illustrated in FIG. 2. Alternatively, the sleeve 20 canbe molded without any ridges or grooves.

Preferably, before initial assembly of the components, the outer body 22is annealed. As an example, the outer body 22 can be heated to atemperature of about 2000 to 2100° F. for a pre-determined period oftime and then permitted to cool to ambient temperature. After thisinitial annealing, the conductor 12 is inserted into the hollow rigidplastic sleeve 20, and the sleeve 20 is inserted into the hollowannealed outer body 22. This places the assembly in condition forcrimping operations, swage-crimping operations, or both, as discussedbelow.

Crimping and/or swage-crimping operations according to the presentinvention are accomplished at ambient temperature thereby permitting useof a wider range of materials for the various components of the device10. The initial annealing step to the outer body component 22effectively reduces the amount of compression forces required during thecrimping and/or swage-crimping operations. The use of a reduced amountof force provides an advantage in that less of the softer materials,i.e., the center conductor 12 and plastic insulator sleeve 20, areextruded and displaced during the crimping and/or swage-crimpingoperations thereby enhancing the ability to form a tight hermetic sealof high mechanical strength between the various components.

The crimping and/or swage-crimping operations are accomplished in thefollowing sequence. First, dual outer crimps are simultaneously formedadjacent the opposite ends of the insulator sleeve 20 via a firstcrimping and/or swage-crimping operation. The locations of these dualouter crimps correspond to the outer diameter grooves 32 and 36 of thesleeve 20. This causes the outer body 22 to deflect and extrude intogrooves 32 and 34 thereby forming the inwardly directed ridges 40 and 44of the outer body. During the dual outer crimping and/or swage-crimpingoperation, the material of the center conductor 12 extrudes into theinner diameter grooves, 28 and 30, of the insulator sleeve 20.

After the dual outer crimps are formed, a separate second crimpingand/or swage-crimping operation is applied relative to the middle outerdiameter groove 34 of the insulator sleeve 20. This creates the inwardlydirected ridge 42 of the outer body 22 and further causes the centerconductor 12 to extrude into the inner diameter grooves, 28 and 30, ofthe insulator sleeve 20. Thus, the grooves 28 and 30 are completelyfilled with the material of the conductor 12 and are without voidspaces.

The purpose of the separate second crimping and/or swage-crimpingoperation is to further compress and displace the polymeric electricalinsulator 20 and conductor 12 after the compressive boundaries have beenformed by the initial dual outer crimping and/or swage-crimpingoperation. The second central crimping and/or swage-crimping operationincreases the compressive load on the plastic insulator 20 and allowsfor larger mismatches in thermal expansion between the components of thedevice 10. The feed-through device 10 made by this process can undergowider temperature excursions with no loss in hermeticity.

The dimensions of one or more ends of the device 10, such as the end 16,may be required to be within tight tolerances. For example, end 16 asillustrated includes a rectangular tip with opposite rectangular flatsurfaces. Maintaining dimensional integrity of end 16 can pose aproblem, since the soft materials of the conductor 12 and/or plasticsleeve 20 will extrude longitudinally out both ends during the crimpingand/or swage-crimping operations. According to the present invention,dimensional integrity of end 16 is maintained by placing end 16 into arestraining cavity or mold during the crimping and/or swage-crimpingoperations to prevent extrusion of material from altering the desired,as-formed shape of end 16.

The grooves 28, 30, 32, 34 and 36 provide a reservoir for the movementof the softer components of the assembly during the crimping and/orswage-crimping operations. The softer more ductile material extrude intothe grooves of the harder component materials thereby forming tightmechanical interlocks between the components of the assembly with novoid spaces. The movement of the material into the grooves results inthe formation of a longer and more arduous labyrinthine path between theconfronting faces of the components of the device 10. In addition, thegroove volumes minimize extrusion of the softer material to furtherensure that outer dimensional stability of the feed-through device 10 ismaintained.

As a final step, the crimped assembly is annealed and/or stress relievedby heating to a temperature below that of the melting point of theplastic insulator sleeve 20. For example, the complete assembly can beheated to a temperature of about or around 100° C. This temperature isselected based on the specifics of the plastic material and can behigher or lower than 100° C. This relieves the internal stresses in theplastic insulator material 20 developed during the crimping and/orswage-crimping operations and further enhances the hermeticity of thefinal assembly of the device 10.

A second embodiment of an electrical feed-through device is illustratedin FIGS. 3 and 4. Unlike the device 10 of FIGS. 1 and 2, the device 50of FIGS. 3 and 4 has a relatively short length thereby eliminating thepossibility of using the crimping and/or swage-crimping operationsdiscussed above.

The device 50 includes a conductor 52 and an annular outer body 54. Theconductor 52 can be centered within the outer body; however, it does notneed to be centered and can be offset relative to the center of theouter body. As examples, the conductor 52 can be made of copper,aluminum, molybdenum, titanium or other material and the outer body 54can be made of stainless steel or other materials. The conductor 52 andouter body 54 are positioned in a mold, and molten plastic 56 is filledin the gap 58 therebetween. Preferably, before the plastic 56 is added,a one-piece or multi-piece rigid insert 60, such as an annular insert,is position within the gap 58 such that it surrounds the conductor 52and permits the molten plastic 56 to flow thereabout to therebyencapsulate the insert 60. See FIG. 4. As an example, the insert 60 canbe made of a ceramic material, a high-temperature plastic material, orthe like.

The insert 60 maximizes compressive forces during the cool down cycle ofthe plastic 56 and densifies the plastic insulator 56 so that higherlevels of hermeticity can be achieved in insulator seals of thin crosssections. In addition, the rigid insert 60 increases the pressurecapability of the feed-through device 50.

A third embodiment of an electrical feed-through device is illustratedin FIGS. 5 and 6. The device 70 includes a plurality of separate metalconductor pins 72 arranged within and extending through a hollow metalouter body 74. As best illustrated in FIG. 5, the illustrated embodimentincludes four conductor pins 72 arranged at twelve o'clock, threeo'clock, six o'clock, and nine o'clock positions about the imaginarycircle “C” (see FIG. 5). Of course, other arrangements of the conductorpins can be used. The conductor pins 72 can be made of copper, aluminum,molybdenum, titanium or other material and the outer body 74 can be madeof stainless steel or other material.

A multi-piece, segmented, rigid insert 76 is also positioned within theouter body 74. The insert 76 can be made of a ceramic material, ahigh-temperature plastic material, or the like. The insert 76 of theillustrated embodiment includes a centered disc-shaped insert 78 andfour outer arcuate-shaped inserts 80. The disc-shaped insert 78 includesfour longitudinally extending grooves 82 through which the conductorpins 72 are located and extend. The arcuate segments 80 are positionedabout the center insert 78 and pins 72 with spacing 84 located betweeneach adjacent pair of segments 80. In addition, each of the arcuatesegments includes a longitudinally extending groove 86 through which oneof the conductor pins 72 is located and extends. Thus, each conductorpin 72 is sandwiched within the outer body 74 between the center insert78 and one of the arcuate segments 80.

The conductor pins 72, insert 76, and outer body 74 are positioned in amold, and gaps 88 are present between the conductor pins 72, segmentedinsert 76 and outer body 74. Molten plastic 90 is filled into the gaps88 and hardened to encapsulate the conductor pins 72 and insert 76within the outer body 74.

As an optional additional step, the assembly of the pins 72, inserts 76,plastic 90, and outer body 74 can be subjected to crimping and/orswage-crimping operations to produce crimps 92 further securing andhermetically sealing the plastic 90 to the outer body 74.

For reasons discussed above, the methods and devices of the presentinvention permit broader selection of materials from which the devices10, 50 and 70 can be manufactured. The broader selection expands thecorrosion resistance capabilities of electrical and RF feed-throughdevices in chemically corrosive environments. In addition, the broaderselection eliminates the need to use dissimilar metals between theelectrical leads and the terminal thereby minimizing galvanic inducedmaterial instability. Galvanic induced corrosion is a limiting factor ofelectrical feed-through devices where long-term seal integrity isdesired.

The design flexibility provided by the present invention is of specialimportance for high voltage lithium-ion cells in that the terminal leadconductor for the positive electrodes are typically aluminum whilecopper is common electrical leads for the negative electrodes. Whenaluminum and copper terminal feed-through devices are used, directwelding can be effected between the respective lead materials. Thispresents an ideal electrochemical condition and is well suited for longlife applications.

The electrical terminal feed-through seal concept of the presentinvention also adapts well to larger electrochemical capacity cells,especially when the electrical terminal must carry high current.Accordingly, the terminal conductors must be relatively large indiameter, typically greater than 0.25 inches in diameter. Thus,scalability to larger size is another advantage of the presentinvention.

Various alternative designs can be utilized. For example, additionalgrooves can be formed in the plastic insulator, or the grooves can beformed in the conductor or outer jacket of the device instead of theinsulator, or no grooves can be provided initially. In addition, thecross-section of the conductor and device is not limited to circular andcan be any shape including, for instance, oval, multi-sided, square,rectangular, diamond-shaped, hexagonal, octagonal, and the like.Further, the conductor can be replaced with an optical rod if an opticalfeed-through device is desired.

While preferred feed-through devices and methods of manufacturing suchdevices have been described in detail, various modifications,alterations, and changes may be made without departing from the spiritand scope of the present invention as defined in the appended claims.

1. A method of making a hermetically-sealed electrical feed-throughdevice, comprising the steps of: positioning at least one conductorwithin a separate outer body in a mold such that a gap is formed betweenthe at least one conductor and the outer body; positioning an insert inthe gap between the at least one conductor and the outer body; fillingthe gap with molten plastic such that the plastic encases the insertwithin the plastic; and permitting the plastic to harden therebyconnecting the at least one conductor to the outer body.
 2. A methodaccording to claim 1, wherein said insert is made of a ceramic materialor a high temperature plastic material, said outer body is made ofstainless steel, and said at least one conductor is made of aluminum,copper, molybdenum or titanium.
 3. A method according to claim 2,wherein said at least one conductor includes multiple, separate,spaced-apart conductor pins, and wherein said insert includes amulti-piece, segmented insert.
 4. A method according to claim 3, furthercomprising the step of crimping and/or swage-crimping the outer body tothe hardened plastic.
 5. A method of making a hermetically-sealedelectrical feed-through device, comprising the steps of: inserting anelongate conductor within a hollow portion of a plastic insulator bodyand the plastic insulator body within a hollow outer jacket to form anassembly; before said inserting step, pre-forming the plastic insulatorbody with a spaced-apart pair of annular circumferentially-extendinggrooves on its inner surface for facing the conductor within theassembly and three spaced-apart circumferentially-extending grooves onits outer surface for facing the outer jacket within the assembly; andafter said inserting step, crimping and/or swage-crimping the assemblyat ambient temperature to cause the materials of the conductor and outerjacket to be displaced and extruded into the pre-formed annularcircumferentially-extending grooves of the plastic insulator bodythereby creating annular circumferentially-extending mechanicalinterlocks between the conductor, insulator body, and outer jacket.
 6. Amethod according to claim 5, wherein said crimping and/or swage-crimpingstep includes: a first crimping and/or swage-crimping operation in whichdual circumferentially-extending crimps are simultaneously formed atopposite end sections of the assembly at locations corresponding to anouter two of the three pre-formed annular circumferentially-extendinggrooves on the outer surface of the insulator body; and a separatesecond crimping and/or swage-crimping operation after said firstcrimping and/or swage-crimping operation, said second crimping and/orswage-crimping operation forming a circumferentially-extending crimp ata location on the assembly spaced from and between said dualcircumferentially-extending crimps and corresponding to a middle one ofthe three pre-formed annular circumferentially-extending grooves on theouter surface of the insulator body.
 7. A method according to claim 6,wherein an exposed end of the conductor is positioned within arestraining mold cavity during said crimping and/or swage-crimpingoperations to ensure that dimensional integrity of the exposed end ismaintained.
 8. A method according claim 7, further comprising a step ofanneal heat treating or stress-relieving the outer jacket before saidstep of inserting the plastic insulator body within the hollow outerjacket.
 9. A method according to claim 8, wherein said outer jacket ismade of stainless steel and is annealed at a temperature of 2100° F.during said anneal heat treating step.
 10. A method according to claim8, further comprising the step of annealing the assembly, after saidcrimping and/or swage-crimping operations, to a temperature below themelting point temperature of the plastic insulator body.
 11. A methodaccording to claim 6, wherein each of said pre-formed annularcircumferentially-extending grooves on the outer face and inner face ofthe plastic is ring-shaped, endless and continuous.